The exact relationship is not yet fully established – Williams, Kay and Kirk (2010) prefer the view that tarsiers and simians share a common ancestor, and that common ancestor shares a common ancestor with the omomyids, citing evidence from analysis by Bajpal et al. in 2008; but they also note two other possibilities – that tarsiers are directly descended from omomyids, with simians being a separate line, or that both simians and tarsiers are descended from omomyids.

[5] Genetically, five short interspersed nuclear elements (SINEs) are common to all haplorhines whilst absent in strepsirrhines.

[4] The haplorhine upper lip, which has replaced the ancestral rhinarium found in strepsirrhines, is not directly connected to their nose or gum, allowing a large range of facial expressions.

[7] The taxonomic name Haplorhini derives from the Ancient Greek haploûs (ἁπλούς, 'onefold', 'single', 'simple') and rhinos (ῥις (genitive ῥινός), 'nose').

It refers to the lack of a rhinarium or "wet nose", which is found in many mammals, including strepsirrhine primates.

[9] The same molecular analysis suggests the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorhines 70 mya.

[4] Kay et al. (2004) point out that a case can be made for Amphipithecidae being placed either as adapiformes (i.e. early strepsirrhines) or as early anthropoids, noting in particular that they had a long evolution separate from other groups, and that key parts of their anatomy are missing from the fossil record.

- finally, they also consider the hypothesis that oligopiths are adapiformes (i.e. early strepsirrhines rather than early haplorhines)[17] Ni et al., in announcing Archicebus achilles in 2013 as what they describe as the earliest known primate with such detailed remains, place it somewhat differently to the above as they place Omomyids within Tarsiiformes, with Omomyids and Tarsiidae sharing a common ancestor, and that common ancestor sharing a common Tarsiiform ancestor with the Archicebidae.